Wake up feeling rested. This free sleep calculator uses 90-minute sleep cycles to suggest the best times to go to bed or wake up — so you finish a cycle instead of being jolted out mid-sleep.
Based on ~90-minute sleep cycles. Waking at the end of a cycle can feel easier than mid-cycle. Cycle length varies by person — use these as a guide.
Use this free sleep calculator to find the best times to go to bed or wake up. Based on 90-minute sleep cycles, it suggests times that aim to let you wake at the end of a cycle rather than in the middle of one.
A sleep calculator works backward (or forward) through 90-minute sleep cycles to suggest bedtimes or wake times. Set when you need to wake up and it shows the best times to fall asleep; set a bedtime and it shows good times to wake. It also allows about 15 minutes to drift off.
Sleep moves through repeating cycles of light sleep, deep sleep and REM, each lasting roughly 90 minutes. Waking at the end of a cycle, in lighter sleep, tends to feel easier than being woken mid-cycle from deep sleep. Most adults do well on 5 to 6 full cycles — about 7.5 to 9 hours.
| Age group | Recommended sleep |
|---|---|
| Teens (14–17) | 8–10 hours |
| Adults (18–64) | 7–9 hours |
| Older adults (65+) | 7–8 hours |
These are general guidelines from sleep health organizations. Individual needs vary.
| Term | What it means |
|---|---|
| Sleep cycle | A ~90-minute round of light, deep and REM sleep. |
| REM sleep | The dream-rich stage important for memory and mood. |
| Sleep latency | How long it takes you to fall asleep. |
| Sleep hygiene | Habits and conditions that support good sleep. |
It counts backward or forward in 90-minute sleep cycles and adds about 15 minutes to fall asleep. So if you need to wake at 7:00 AM, good bedtimes are around 9:45 PM (6 cycles) or 11:15 PM (5 cycles).
A full sleep cycle averages about 90 minutes, moving through light sleep, deep sleep and REM. It varies by person and night, so treat the timings as a helpful guide rather than an exact rule.
Most adults do best with 7 to 9 hours — roughly 5 to 6 complete cycles. Teens generally need more, and individual needs vary.
Waking in the middle of a deep-sleep stage can leave you groggy even after a long night. Aiming to wake at the end of a cycle is meant to reduce that mid-cycle grogginess.
No — total sleep, consistency and sleep quality all matter. The cycle timing is one helpful tool, not the whole picture. Persistent sleep issues are worth discussing with a professional.
Yes, this sleep calculator is completely free, needs no sign-up, and gives instant results directly in your browser.